A lattice constant formatted epitaxial template for light emitting devices includes a starting epitaxial template having a base, a plurality of alternately arranged protrusions and depressions on the base; first material portions epitaxially formed on top of the protrusions and second material portions epitaxially formed in the depressions, wherein lattice constants of the first material portions on the protrusions are different from those of the second material portions in the depressions. A method for making a lattice constant formatted epitaxial template is provided. Also provided is a light emitting device containing a lattice constant formatted epitaxial template.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A light emitting device comprising: an n-type layer; a p-type layer; an active region sandwiched between the n-type layer and the p-type layer; and a lattice constant formatted epitaxial template; wherein the lattice constant formatted epitaxial template has a growing surface on which the n-type layer grows, and the growing surface comprises a plurality of first material portions and a plurality of second material portions with each of the first material portions being alternately arranged with each of the second material portions, and wherein lattice constants of the first material portions are different from those of the second material portions.
2. The light emitting device according to claim 1 , wherein each of the first material portions and each of the second material portions are of lateral dimension from 100 nm to 3000 nm in at least one lateral direction, respectively.
3. The light emitting device according to claim 1 , wherein the first and second material portions are made of AlGaN, the Al-composition of the first material portions is higher than the Al-composition of the second material portions, thus the lattice constants of the first material portions are smaller than those of the second material portions.
4. The light emitting device according to claim 3 , wherein the n-type layer is made of AlGaN, the Al-composition of the n-type layer is lower than the Al-composition of the first material portions and higher than the Al-composition of the second material portions, thus the lattice constants of the n-type layer are larger than the lattice constants of the first material portions and smaller than the lattice constants of the second material portions.
5. The lattice constant formatted epitaxial template according to claim 1 , wherein there is a height difference between the first material portions and the second material portions in a layer growing direction, and the height difference is larger than 100 nanometers.
6. Light emitting device according to claim 1 , wherein the n-type layer is an n-type AlGaN layer and the active region emits ultraviolet emissions in the wavelengths of 230-365 nm.
7. A lattice constant formatted epitaxial template comprising: a starting epitaxial template comprising a base, a plurality of alternately arranged protrusions and depressions on the base; first material portions epitaxially formed on top of the protrusions and second material portions epitaxially formed in the depressions, wherein lattice constants of the first material portions on the protrusions are different from those of the second material portions in the depressions.
8. The lattice constant formatted epitaxial template according to claim 7 , wherein the protrusions are arranged on the base in a one-dimensional or two-dimensional periodic pattern, and the protrusions are of lateral dimension of 100-3000 nm, height of 200-1500 nm and pitch of 200-3500 nm.
9. The lattice constant formatted epitaxial template according to claim 7 , wherein the lattice constants of the first material portions are smaller than those of the second material portions.
10. The lattice constant formatted epitaxial template according to claim 7 , wherein the starting epitaxial template is made of MN, and the first and second material portions are made of AlGaN, wherein the Al-composition of the first material portions is higher than the Al-composition of the second material portions, thus the lattice constants of the first material portions are smaller than those of the second material portions.
11. The lattice constant formatted epitaxial template according to claim 7 , wherein the starting epitaxial template is made of GaN, and the first and second material portions are made of AlGaN, wherein the Al-composition of the first material portions is higher than the Al-composition of the second material portions, thus the lattice constants of the first material portions are smaller than those of the second material portions.
12. The lattice constant formatted epitaxial template according to claim 7 , wherein the starting epitaxial template is made of AlGaN, sapphire, SiC, or Si, and the first and second material portions are made of AlGaN, wherein the Al-composition of the first material portions is higher than the Al-composition of the second material portions, thus the lattice constants of the first material portions are smaller than those of the second material portions.
13. The lattice constant formatted epitaxial template according to claim 7 , wherein the first and second material portions are simultaneously formed on the protrusions and in the depressions, respectively, from the same feed material via composition segregation.
14. The lattice constant formatted epitaxial template according to claim 7 , wherein there is a height difference between the first material portions and the second material portions in a layer growing direction, and the height difference is larger than 100 nanometers.
15. A light emitting device comprising: an n-type layer; a p-type layer; an active region sandwiched between the n-type layer and the p-type layer; wherein the n-type layer contains first portions and second portions alternately arranged along a lateral direction of the n-type layer, and lattice constants of the first portions are smaller than lattice constants of the second portions.
16. The light emitting device according to claim 15 , wherein each of the first portions and each of the second portions has a lateral dimension from 100 nm to 3000 nm in at least one lateral direction, respectively.
17. The light emitting device according to claim 15 , wherein the n-type layer is an unrelaxed layer.
18. The light emitting device according to claim 15 , wherein the n-type layer is a fully relaxed layer, and the first and second portions are formed within a sublayer of the fully relaxed n-type layer.
19. The light emitting device according to claim 15 , wherein the n-type layer is a AlGaN layer or an InGaN layer.
20. A light emitting device comprising: a p-type layer; a light emitting active region; and the lattice constant formatted epitaxial template according to claim 7 ; wherein the active region is directly formed on the first material portions and the second material portions of the lattice constant formatted epitaxial template.
21. The light emitting device according to claim 20 , wherein the first and second material portions are made of InGaN and the In-composition of the second material portions is higher than that of the first material portions.
22. The light emitting device according to claim 21 , wherein the active region is made of InGaN light emitting quantum wells for emitting visible light.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
March 27, 2015
October 18, 2016
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